Battery Tender hook-up

[LAKERtoo]

.. I picked up a Noco Genius G1100 Battery Charger/Tender to hook up to the 2 batteries in my R21 Classic for the winter .. the batteries are hooked up in the common configuration where the switch can set them to OFF/ONE/BOTH. When they are set up like this, my assumption is that I connect one of the ring connectors to the negative post on one battery and the other to the positive on the second .. so 1) does it matter which battery I put the negative connection on and 2) .. what position should I leave the battery switch ? off, or both ?? Thanks for any input ..Rob

 

[knotflying]

Put your switch to both and hook up the positive and negative on the same battery.

 

[LAKERtoo]

Thanks for the reply .. so the fact that they are hooked up in parallel allows both to be charged with BOTH selected on the switch ??

 

[SGIDAVE]

Thanks for the reply .. so the fact that they are hooked up in parallel allows both to be charged with BOTH selected on the switch ??

That is correct. It's the same as when you are underway with the Yanmar's alternator charging both batteries (when the selector switch is on "both").

Dave

 

[BradOwens]

The prior posting is correct. If you connect to the positive on one battery and the negative on the other battery, you have now created a 24 volt circuit. That would be bad!

 

[SGIDAVE]

Hello Rob,

Alternatively, you could also hook the Noco pos ring terminal to the post on the back of the A/B/Both/OFF switch that your alternator wire is connected. Then, leave the switch in BOTH position to keep both batteries topped for the winter. In the spring, unhook and coil up the Noco harness until next winter. Maybe that would be a neater install than messing with the battery terminals.

dave

 

[SGIDAVE]

The prior posting is correct. If you connect to the positive on one battery and the negative on the other battery, you have now created a 24 volt circuit. That would be bad!

Probably be OK. NOrmal set up with A/B/Both/OFF switch is for the battery negative terminals to be TIED into a single negative buss. So, the charger's neg connection could go to EITHER battery as long as they are already electrically connected.

dave

 

[BradOwens]

I'll do some more checking, but I believe connecting to Neg on one battery and Pos on the other will create a series connection vs parallel. Two batteries in series double the voltage (bad), two batteries in parallel double the amperage (good).

 

[SGIDAVE]

I'll do some more checking, but I believe connecting to Neg on one battery and Pos on the other will create a series connection vs parallel. Two batteries in series double the voltage (bad), two batteries in parallel double the amperage (good).

Hello Brad,

Correct, connecting two batteries in series DOUBLES the voltage (not capacity) whilst parallel connections doubles the capacity not voltage.

But for SERIES connection to occur, the NEGATIVE terminal of one battery must be connected to the pos on the second battery. That's not happening in Rob's tug; the neg terminals of both batteries are tied together. In this arrangement, he can connect the NOCO's pos ring terminal to either battery OR the lug on the A/B/OFF/BOTH switch to which the Yanmar's alternator is connected. Doing the latter will simulate the normal charging situation as if the engine were running. Both batteries MUST be electrically connected to the SAME ground (ultimately the engine) to complete a circuit for the alternator to charge them....I THINK anyway 😉

When you turn the battery switch to BOTH, they are effectively in a PARALLEL arrangement, so...they must share a common ground. I'm not an electrician nor did I sleep at a HOliday Inn recently, so this is just one Tugnut's opinion.

dave

 

[CAPTCRUNCH]

NOCO's website provides a video on how to charge two batteries in parallel (as when the battery switch is in the "both" position: http://www.geniuschargers.com/video/cha ... n_parallel
As the video states, the two batteries' capacities are combined when doing this, which leads me to wonder if your charger - intended for a single motorcycle battery, per NOCO - will be up to the job. I guess you could improve things by periodically switching between single, isolated batteries and leaving the switch in the "off" position so you aren't powering the whole boat.

 

[daviduphoff]

Hello Rob,

Alternatively, you could also hook the Noco pos ring terminal to the post on the back of the A/B/Both/OFF switch that your alternator wire is connected. Then, leave the switch in BOTH position to keep both batteries topped for the winter. In the spring, unhook and coil up the Noco harness until next winter. Maybe that would be a neater install than messing with the battery terminals.

dave

This is what I did on my 18 and it works great. I can also switch between the batteries to charge if need be. I have the wiring permanently installed.

David

 

[LAKERtoo]

arghh .. the more I read the more options there seems to be .. the NOCO video on charging 2 batteries in parallel indicates that ( regardless of cabin battery switch position) if the ring connectors are hooked up to the negative on one battery and the positive on the other, that both batteries will be charged and monitored .. it will just take longer to come to full charge .. this sounds like the cabin battery switch should be OFF in case any draw or short somewhere ?? and the charge and monitoring will still proceed regardless of switch position ?? .. is the switch position a factor ?? Rob

 

[knotflying]

You may be over thinking this. I assume you just have two batteries, house and engine? If that is the case then they will not be connected in parallel. They will only be in parallel when you throw your switch to both. If the house battery has a house switch then turn that off and that should eliminate any potential large items that may be running and causing a draw.

 

[CAPTCRUNCH]

Sorry if I added to the confusion. The fundamental arrangement for charging your two batteries with your charger is really very simple; the choices are mostly a question of how to deliver the charging current into the basic circuit. I believe the bottom line is that your proposal in your original post will work IF you put the battery switch in the BOTH position. It won't matter which positive battery terminal you connect the charger to; they will be connected through the switch. Nor will it matter which negative battery terminal you connect to; they are already connected by the boat's wiring. The "Dave-and-David" arrangement described above is a more elegant way of doing the same thing. I would certainly want to periodically check the status lights on the charger to see how it's doing so you won't be surprised next Spring.

 

[oscar]

If you want to be absolutely sure there is no electricity disappearing into the system, you can have all switches off, connect the charger to one bank, and then connect the two banks with a light set of jumper cables.

 

[SGIDAVE]

My personal preference is to have power to the boat's systems OFF when she is unattended. Thus, I prefer NOT to leave that switch on BOTH whilst she's tucked away for extended periods. What I've done on other boat's with a 2 battery system and A/Both/B/Off switch was to wire in TWO maintainers. Little ones like this are water resistant and come with long enough cords that the little box-part hangs outside the hull so you can easily check the lights for proper functioning without uncovering the boat or climbing inside. Like this:

It's called a Battery Tender. Yes, very low output but plenty to maintain your boat's batteries using smart charging technology. I'm sure there are other brands that do the same thing.

Now, what I'm suggesting is just MY approach. Using ONE maintainer-charger for the winter can be made to work fine as detailed in the numerous posts above. I'm sure millions of boaters have left their boat's DC circuits energized for months whilst unattended without trouble...and then there's the few who had something BAD happen.

We all choose our own risks

dave

 

[CAPTCRUNCH]

Amen! Seacocks closed, switches off. Haven't lost a boat yet...a few batteries, but no boats.